You might add to the onclick action of the submit button:
METHOD(Object='q',Method='DisableInput')

Then in the first slide add an action beforeDisplay:
VARIABLE(Name='scoreCounter',Value='0',Scope='Entire Module')

and at the right IF condition on the onclick of the submit button:
VARIABLE(Name='scoreCounter',Value='#scoreCounter+1',Scope='Entire Module')

Now each correct answer adds 1 to your own variable 'scoreCounter'.
In the end of your course / test you can use the value of scoreCounter.
On a slide make an object 'Simple Textbox', identifier myText. Enter the text 'your score is:'.

This slide's action afterdisplay:
METHOD
Object='myText'
Method='Add Text'
Where to add: At the end
Adding style: One paragraph
Text to add: #scoreCounter